textproduct: Rapid City

KEY MESSAGES

- Isolated to scattered showers and thunderstorms expected Sunday, with the early morning and mid-to-late afternoon periods looking most active.

- Cold front drops through Monday, bringing gusty winds.

- Mean northwest flow aloft brings unsettled weather through much of next week.

UPDATE

Issued at 1025 PM MDT Sat May 2 2026

Massaged the latest NBM PoPs and QPF in the forecast for tonight and Sunday, mostly to lightly tamper down any convective contamination/bullseyes and keep amounts light, while reducing PoPs over the Black Hills region to generally fall under 50% and also broadbrush light PoPs outward to give slightly better areal coverage to mentions of showers and storms. All of this better encompasses the range of solutions in the latest HREF CAMs and better reflects the showery nature of this activity. Still expecting some potential for elevated embedded thunder overnight, and then perhaps a decent storm or two Sunday afternoon generally from northeast WY down across the Black Hills into the southwest SD plains, although limited CAPE still seems like a limiting factor. Still, model soundings show as much as 800 J/kg SBCAPE along with some DCAPE and steep low-level lapse rates with a relatively dry surface, and at least 25kts of deep-layer shear. A couple storms may produce wind gusts of 40-50 MPH.

DISCUSSION

(This Evening Through Saturday) Issued at 1242 PM MDT Sat May 2 2026

18z surface analysis had low over northeastern ND with cold front into far northern WY/northwest SD, just entering the far northwest reaches of the CWA. Water vapour matinee had northwest flow aloft with a couple of weak embedded shortwaves heading for the northern Plains. Not much CU per 0.5km visible loop early this afternoon (even with well-mixed 18z KUNR sounding - it is quite dry), but weak wave over ND should assist a few more CU and the potential for isolated -shra later this afternoon over central SD.

Tonight, cold front exits the CWA with weak cold air advection. Behind it ahead of weak shortwave, expect a narrow band of weak 800-600mb frontogenesis/theta-e advection and a touch of MUCAPE. Should be sufficient for weak elevated convection across northeastern WY/west-central SD overnight. SPC HREF paintballs support.

Precipitation should wane Sunday morning, but additional -shra/TS will develop in the afternoon per mean 500J/kg SBCAPE and limited SBCIN. Black Hills likely the origin given terrain influence, confirmed by HREF. Modest 0-6km bulk shear could pop an active storm or two, but weak buoyancy will limit potential. Convection dies down Sunday night.

Second cold front arrives Monday with a stronger embedded shortwave. Result will be some showers along with gusty northwest winds per probabilistic guidance (40-60% chance 45mph gusts from K2WX-KRAP), although isallobaric forcing isn't that impressive. Can't rule out a few lightning strikes as well as some snow mixing in up high, but impactful snow accumulation is not expected.

Tuesday through Saturday, northwest flow aloft will bring a series of disturbances/fronts through the CWA. Temperatures 5-10F below normal Tuesday rising to 5-10F above by Saturday.

AVIATION

(For the 12Z TAFS Through 12Z Monday Morning) Issued At 521 AM MDT Sun May 3 2026

Isolated to scattered showers will continue through the afternoon from northeastern Wyoming through the Black Hills area through southwestern South Dakota. A few thunderstorms may develop this afternoon, as well. Otherwise VFR conditions are expected through the forecast period.

FIRE WEATHER

Issued At 1242 PM MDT Sat May 2 2026

Near critical fire weather conditions will continue this afternoon per minimum relative humidity in the teens and west (ahead of cold front)/northwest winds (behind cold front) at 15- 25mph.

UNR WATCHES/WARNINGS/ADVISORIES

SD...None. WY...None.